I agree that most altcoins have no intrinsic value yet, their utility apps haven't been developed or do not perform the desired function. So most of them will be worthless...just like in the .com bubble, where most web based firms dissapeared.
Some applications, some blockchain uses will become widespread. Those apps, like for instance dtube on steamit using ipfs, try to become ad free, censor free you tube replacements that also reward their content creators.....but these daps have to become more user friendly, and that is difficult, especially as it's only a couple of developers working on them, and youtube has a plethora.
As a permaculture currency I would envisage a kind of lets system where the local would be permies, so a permaculture exchange trading system...pets...
It could be used in lieu of the apples...create a market, digital and real world, for services, seed exchanges, courses....
We are at very early stages of these developments, payments in cryptocurrency are becoming fast and almost fee less, like cointext that uses sms texting from any phone without any intermediary...
As for the arguments made that if there is no electricity, crypto does not exist anymore...it would be necessary for that to happen that the whole earth be without electricity, and I think we'd have other worries by that time.
Also, about the loss of cryptos, there is a lot of redundancy you can put into safeguarding your coins...you just have to have the discipline to do it...
I think we would be stacking functions if we could add these new technologies...